Multi-strand, abrasion resistant electrical conductors



R. HOHN June 30, 1959 MULTI-STRAND, ABRASION RESISTANT ELECTRICAL CONDUCTORS Filed March 8, 1955 N "H MM x 5 g United States Patent "ice MULTI-S'IYRAND, ABRASION RESISTANT ELECTRICAL CONDUCTORS Robert Hiihn, Neuss am Rhine, Germany Application March 8, 1955, Serial No. 492,955

Claims priority, application Germany March 18, 1954 2 Claims. (Cl. 174-8) This invention concerns multi-strand electrical conductors and aims to provide an improved flexible conductor which is less susceptible to wear than those previously proposed.

The electrical leads of electrical gear, such as welding, soldering, testing instruments, eleetro-magnets and so on, which are employed in mass production techniques, on conveyor belts, on travelling tables, in machine tools, and in similar circumstances, sometimes undergo many thousand bending flexions during one working shift. This abnormal stressing, which seldom occurs in other industrial fields, causes a very rapid wear of the conductors in these leads and these conductors therefore often have a life of only a few weeks or months. Experiments have shown that the rapid wear of the conductors is mainly attributable to breakages of the copper wire in the conductors.

In the majority of instances these conductors are multistrand conductors comprising concentric layers of intertwisted wires or groups of wires and at every flexion of the conductor there is a small relative movement between the wires, or the groups of wires, so that the various concentric layers continually Iub against one another and wear out at the points of frictional contact until finally there is a complete break in the wires. Once individual wires have broken, the conductor quickly becomes. wholly useless.

Such wear in the wire is particularly accelerated if additional fields of force become effective in the conductor. Thus, for example in the production of automobile vehicle bodies, it is customary to employ spot welding appliances in which, in use, a very high number of current impulses of thousands of amperes is produced in quick succession.

The abnormally large magnetic eifects of these impulses, which are visible externally of the conductor, naturally also have a powerful effect on the layers of wire in the conductor.

In the industry concerned with the use of twisted wire ropes or cables for conveying purposes it is known, during the normal twisting procedure, to run into wire ropes which are intended to undergo tensional strains strands of fibrous material, mostly in combination with lubricating materials, as a core or to pack or fill up the gaps in the twisted rope. This expedient improves the flexibility and ductility of the rope, but over a period does not eifectively serve as a means for preventing wear, since afiter lengthy use of the rope the volume of the added material becomes smaller and it therefore no longer serves properly to space the wire parts of the rope from one another. Moreover such packing material, if applied to an electrical conductor, would increase its diameter to an undesirable degree. To obtain a complete solution to the problem, particularly if additional magnetic field effects are also set up in the conductor, a more effective arrangement of packing is required.

The present invention aims to oppose the wear of the Patented June 30, 1959 soft and thin strands of copper wire in electrical conductors by preventing the rubbing of metal on metal at the critical parts within the conductor and so arranging wear-resistant material as an intermediate packing that it provides all-round spacing of the parts of the conductor by effectively spacing the wires and/or twisted layers of wires at all sides from one another.

Thus, according to this invention there is provided a flexible multi-strand electrical conductor comprising a plurality of concentric layers of electrically conductive wires and/or groups of wires and an intermediate layer of non-fibrous, wear-resistant packing material disposed between adjacent conductive layers so as to prevent frictional contact between and consequent wear of such conductive layers.

The said packing material should not be of a fibrous character and moreover, must be rotand abrasion-resistant since conductors are often water-cooled in view of the high load current intensities which they have to carry. To this end packing materials of a polyamide or polyurethane or similar basis, or mixed polymers, for example of polyvinylidene chloride and vinyl chloride, which are known to have a high resistance to rubbing and wear, have proved to be particularly advantageous.

The packing material may conveniently be wrapped around each layer of twisted wires and may be in the form of strips or continuous injected or extruded single filaments of circular section; thus for example, the packing may be arranged in open spirals or, as an open braid structure.

According to a further feature of the invention individual, or all the, wires of the multi-strand conductor may be provided with this polyamide or polyurethane packing and then twisted together.

In the case of water-cooled conductors, in which the conductor is situated within the cooling water sleeve of a .plurality of twisted component conductors, each of these component conductors will have a packing of one of the forms indicated, so that the deforming impact effects of the induced magnetic field cannot affect them detrimentally.

Further advantageous details of the invention are indicated in the accompanying drawings, given by way of example, and in which:

Figure 1 shows one embodiment of a conductor according to the present invention; and

Figure 2 shows a further embodiment of a conductor according to the invention.

In the drawings, each embodiment comprises an electrical conductor including a core and two concentric layers 2 and 3 of multi-strand form disposed therearound.

In the embodiment illustrated in Figure 1, an open spiral 4 is employed as the packing for the core 1, whilst an open stn'p braid structure 5 is used as the packing material for the inner layer 2.

Figure 2 shows a further embodiment of the invention in which the core 1 and the alternate wires of the outer layer 3 are provided without an intermediate layer of packing material, whereas all the wires of the inner layer 2 and the alternate wires of the outer layer 3 are covered with an open structure of solid and extruded filaments 7 of circular section, so that despite the fact that there is only a partial employment of packing material, nevertheless there is no possibility of the metal of one wire rubbing on the metal of another wire at any point between layers of the multi-stranded conductor.

As has been stated above, in accordance with the invention materials with a polyamide, polyurethane or a similar base, or materials with a base of suitable wearresistant mixed polymers, can be used to constitute the intermediate layers of packing material 4 to 7.

'I claim:

1. A highly flexible electrically conductive cable for use in a water cooling sleeve comprising a plurality of electrically conductive multi-strand wires disposed closely adjacent each other in concentric layers, said concentric layers having therebetween thin, open and pervious layers of highly rot and abrasion resisting plastic material selected from the group consisting of ,polyamide and polyurethane affording passages for cooling liquid to How through the cable and preventing frictional contact .and wear between adjacentconductive strands of wires, said plastic material being disposed in open helically wound strips and said multi-strand concentric layers being disposed around a core.

2. The combination set forth in claim 1 wherein :said plastic material comprisesopenbraidedmonofil threads.

References Cited in the tile of this patent UNITED STATES PATENTS OTHER REFERENCES Du Pont Product Engineering Bulletin 2, 1955 copy in Scientific Library and in Div. 69. (8 pages, page 2 relied upon.) 

1. A HIGHLY FLEXIBLE ELECTRICALLY CONDUCTIVE CABLE FOR USE IN A WATER COOLING SLEEVE COMPRISING A PLURALITY OF ELECTRICALLY CONDUCTIVE MULTI-STRAND WIRES DISPOSED CLOSELY ADJACENT EACH OTHER IN CONCENTRIC LAYERS, SAID CONCENTRIC LAYERS HAVING THEREBETWEEN THIN, OPEN AND PERVIOUS LAYERS OF HIGHYL ROT AND ABRASION RESISTING PLASTIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF POLYAMIDE AND POLYURETHANE AFFORDING PASSAGES FRO COOLING LIQUID TO FLOW THROUGH THE CABLE AND PREVENTING FRICTIONAL CONTACT AND WEAR BETWEEN ADJACENT CONDUCTIVE STRANDS OF WIRES, SAID PLASTIC MATERIAL BEING DISPOSED IN OPEN HELICALLY WOUND STRIPS AND SAID MULTI-STRAND CONCENTRIC LAYERS BEING DISPOSED AROUNG A CORE. 